This invention relates to a tensioning mechanism for the skins of percussion instruments and consists of threaded bushings held in bearing blocks disposed on the periphery of the instrument wall and of screws which are adjustable therein and which also act on the hoop which holds the skin.
Tensioning mechanisms of this type have already been known for a long time. They have also proved satisfactory in those cases where, with the aid thereof, the skins are stretched so as to be tightly drawn with great force over the rim of the instrument wall. On account of the high tension inherent in the skins, a high frictional force is in fact produced between the turns of the screw and the threaded bush and, as a consequence, the self-locking action is strengthened against an unintentional loosening of the screws.
However, the modern forms of music and especially beat music sometimes require loosely-tensioned skins. The low frictional force which results from this between the threads of the screw and the threaded bush does, however, lead to the disadvantage that the screws easily become automatically loosened, whereby the adjusted tension of the skin is lost.
Accordingly, so as to avoid these disadvantages, locking nuts with a peripheral knurling have been associated with the tensioning mechanisms consisting of the threaded bushes and the screws, so as to maintain the position. It is certainly possible by this means to avoid the undesirable loosening of the tensioning screws in the threaded bushes. Nevertheless, the disadvantage which arises from the use of the locking nuts is that, initially, all locking nuts must be loosened for the purpose of a required change in the skin tension before any adjustment of the tensioning screws can be carried out. After making the required adjustment, it is then necessary for all locking nuts to be tightened once again until they are sufficiently tight.
It is quite evident that, when using this known construction of the tensioning mechanisms, intricate and time-wasting manipulations must be carried out to change the head tension.
The present invention seeks to obviated all the disadvantages which are inherent in the known tensioning mechanisms of the type previously described. Accordingly, the invention seeks to provide a tensioning mechanism which permits a direct adjustment of the screws for the purpose of a required variation in the head tension, but in addition also offers a high degree of security against unintentional loosening of the screws in the threaded bushings.
According to this invention, a tensioning mechanism is provided for the head of a percussion instrument, comprising threaded bushings held in bearing blocks disposed on the circumference of the instrument wall and screws which are adjustable in the bushings and which also act on a hoop which holds the head. Each threaded bushing is formed on its circumference with at least one tangential slot in which a peripheral section of a spring ring engages with a selected tension. Each screw is provided on its shank at least one peripheral flat portion or indentation as a catch surface for that peripheral section of the spring ring which lies in the slot of the threaded bush.
It has been found that the cost of manufacture, as compared with the original type of construction of tensioning mechanisms is only slightly increased by the system of the invention is used; it is clearly lower than the cost for tensioning mechanisms which are fitted with locking nuts.
With regard to the tensioning mechanism constructed in accordance with the invention, it has proved to be particularly advantageous that a form-locking arrangement of the screws in the threaded bushings is produced, instead of a connection that is strictly force-locking. The form-locking securing action is capable of being influenced in a particularly favorable manner by providing the spring ring with a peripheral section having a chordal engagement in the slot of the threaded bush.
It is also preferable that the screw be provided on its shank with a plurality of peripheral flat portions, so as to be able to effect a finely graduated variation in the skin tension.
Preferably, the spring ring is formed of wire or strip material to have approximately the form of a triangle which is open at one point. Preferably, those sides of the triangle which adjoin the opening are given a convex curvature.
Preferably, the tangential slot and the spring ring which is latched therein are arranged on that end of the threaded bush which projects from the bearing block toward the hoop.
With these and other objects in view, as will be apparent to those skilled in the art, the invention resides in the combination of parts set forth in the specification and covered by the claims appended hereto.